Python port of the script (originally written in Java, and later in VBA) used for this article: "Palanisamy N, Osman N, Ohnona F, et al. Does antiretroviral treatment change HIV-1 codon usage patterns in its genes: a preliminary bioinformatics study. AIDS Res Ther. 2017;14(1):2. Published 2017 Jan 7. doi:10.1186/s12981-016-0130-y"